I am 22 and he is 26. We have been together for nearly 4 years... I've tried seducing him, talking to him, joking about it, crying about it and still he never makes an effort. When we first got together things were great... but... he was sexting another girl? Did this turn him on more? I'm at a loss... it's even worse that apart from this he is perfect... is it me?

There is someone else, or otherwise he wouldn't feel this way. It can happen, even after four years. He is not being completely honest with you, but I don't have a cystal ball. Other then that, if it isn't another woman, then you really must sit own and talk to him about his health.